Integrated circuit (IC) devices typically include circuit elements such as transistors, capacitors and resistors formed within or on a semiconductor substrate. Interconnect structures are used to electrically couple or connect the discrete circuit elements into functional circuits. Typical metal interconnects may include a line portion and a via portion.
Interconnect structures may be fabricated from copper, and may include a barrier layer such as titanium or tantalum or nitride materials such as tantalum nitride or titanium nitride, or a combination thereof (e.g., tantalum nitride/tantalum (TNT)). A problem with utilizing copper interconnect structures is that they are highly susceptible to electromigration which can lead to void formation and failure.
Tungsten metallization has been successfully used to fabricate front end contacts and, thus, has been suggested for back end metallization for interconnect fabrication. A desirable advantage with utilizing tungsten metallization is that it is highly resistant to detrimental electromigration effects. However, a disadvantage with utilizing tungsten metallization is that its electrical resistivity is higher than copper. More specifically, tungsten line resistances are 4 to 6 times higher than copper interconnects, and via resistances can be as much as 20% higher. These high resistances severely degrade IC performance and are therefore undesirable.